Surging at idle

[dfws2k]

My car is surging at idle, engine will go up to 2000, then back to 1000.

Car was recently hydrolocked, oil changed 5 times and it started looking like oil again finally after the 4th time.

Car was originally throwing a P0505 code, i think there was still water in the intake manifold and after awhile escaped through the IACV valve. Car no longer throws any codes.

Surging only happens at idle, I haven't changed the spark plugs yet, I plan on it, but i don't think that will solve the surging problem? They looked ok, but they were sitting in water for about a day.

Any ideas on the surging? maybe it is just the sparkplugs?

-Val

[hecash]

You may wish to check your vacuum lines to make sure that one has not been knocked loose while you did this work?

[dfws2k]

All vaccuum lines are where they are supposed to be, and when they aren't, it throws a code within a minute of startup, in my experience.

Thanks for the tip though!

[repiv]

Surging idle is likely due to the sensors inability to see a constant vacuum or manifold absolute pressure or both. You MAP sensor may have been damaged and the air passageway the is under it my be in need of cleaning out. If you remove the MAP sensor, you will see a hole. That's one end of the passageway. If you take off the intake tube, you should see another small hole on the side of the throttle body. That's the other end. You should make sure there's nothing in that passageway. A shot of WD-40 down the hole and a blow dry with air should do the trick. Catch the blow out with a rag.
It would appear that your Idle Air Control mechanism is still contaminated. This should be taken apart and cleaned thoroughly and dried and re-assembled.
How bad was it hydrolocked? Do you know that no piston or rod damage occured?

[dfws2k]

I don't know how to rank the severity of hydrolock, engine was only at ~1500 rpms, no abnormal sounds when it is running, I had a couple technicians listen to it and help me get it started after the hydrolock, and they said it didn't sound like there was any damage.

I will look at the MAP sensor and Idle Air Control mechanism when I change out my sparkplugs, hopefully this weekend. Thanks for the new things to try!

[dfws2k]

Replaced the spark plugs on Saturday, ran the car around for ~an hour. Surging is gone, guess it was something to do with them being old + sitting in water for a little while, most of the electrodes did look pretty nasty.

So everything is great now, VTEC feels good.